Why you should never weigh a hot object?

Question

i am doing a chemistry lab and this was one of the question on my review,and it says it in the packet that you should never weigh a hot object but it doesn't tell why.

Answer 1

first of all because of safety. handling hot objects just isn't as safe as handling room temperature objects.

also, hot objects will radiate heat in the form of convection currents, making slight changes (instabilities) in your readings. this is very noticeable in highly accurate digitial scales used in most modern laboratories.

Answer 2

As air is warmed, the energy from the heat causes the molecules of air to move faster and farther apart. This means the mass is less dense than if the item was cold (where the molecules are close and compact).

Might also come from the fact you don't want to put any hot item on a scale as it would ruin the scales (especially if using a digital scale)... :)

Answer 3

not so particular it truly is authentic. i recognize that in analytical we were taught to "weigh to consistent mass" the position we would want to warmth and weigh till no major weightloss became recorded. We were inspired to weigh even as the crucible became warm. this may be incorrect technique, yet i am going to't imagine that the rigidity of escaping warmth pushing down on the textile might want to be major even as balanced against moisture absorbed from the air once the textile had cooled.

Answer 4

A hot object will heat the air around. it Since hot air rises, the hot object will create a small air current around it. This air current will be detected by the balance, thus giving you a wrong value.

Answer 5

Because convection currents will cause the readings to be unstable. This effect can give significant errors even when the object is only a few degrees above room temperature.

Answer 6

Very true. Convection currents from the hot object cause the readings to be unstable.

Answer 7

From what I remember it was because the cooling causes air currents which would effect the accuracy of the measurement. Convection would apply force on the weighing surface.
I believe it is due to the accuracy required, let's say to .001 gram.
Any air current would effect the reading.

Answer 8

A hot object will expand and possible weigh more or less (according to the material and lab conditions) as it cools.
Liquid is another example which will weight more in the liquid stage than in the gas stage in the same closed container.
Some metals change densitiy when heated and will weight less. sometimes th ereason is loss of gases due to heating.

Answer 9

Next time your in lab go ahead and put a hot substance on the balance. Watch as it cools - the weight will decrease. This is why you should always wait until it is cooled so you get an accurate reading.

Answer 10

Since its hot it might have a different mass than when you originally weighed it at room temperature.